Evaluation of dielectric fluids for macro-scale electrostatic actuators and machinery

Recently interest towards electrostatic actuators and machinery has increased for use in MEMS, mechatronics and renewable energy applications. Effective electromechanical power conversion using electrostatics requires dielectric fluids whose permittivity and breakdown field strength can facilitate adequate electric shear stress and pressure beyond the capabilities of media such as air or vacuum. This paper discusses design points for practical electrostatic force production and evaluates available dielectric fluids in terms of electric shear stress and pressure capability. Key dielectric properties including relative permittivity and breakdown field strength are measured via custom test stand. Attractive force is measured between two electrodes mounted on load cells inside a tank filled with a dielectric liquid. Electrode surfaces may be configured to facilitate electric pressure or shear measurement. Measurements demonstrate fluids capable of reaching several PSI of electric pressure while correlating with analytical and finite element (FE) models, ultimately forming a base for electrostatic actuator/machine design.